1. Field of the Invention
The present invention relates generally to electronic systems and more specifically to interconnections between subassemblies of an electronic system.
2. Discussion of Related Art
Optical interconnections are known in the art. Optical fibers are used in networking and electronic systems to carry large amounts of data. However, it has traditionally been difficult to make connections between optical fibers. Misalignment of the fibers or contamination of the mating surfaces of the fiber can significantly degrade the performance of the optical data link.
In many applications, optical fibers are joined by a splice, which is intended to be a permanent connection of the fibers. However, there are many applications where a separable connection between optical fibers is desired. In these applications, it would be desirable if connections to an optical fiber could be made as easily as a connection to a traditional wire cable carrying electrical signals. For these applications, optical connectors have been developed. The optical connectors allow cables to be joined, thus acting as a separable splice for optical fibers to be connected to a circuit board or other assembly.
Optical fibers are sometimes used to route signals between circuit boards in an electronic assembly. In these applications, the optical fibers are configured much like a traditional backplane connector in an electronic assembly, allowing boards to be inserted or removed from the assembly.
FIG. 1 shows a portion of an electronic system 100 in which signals are carried through optical fibers, such as those illustrated at 150 and 152. Backplane 100 has multiple backplane connectors 112A and 112B mounted to it. Fibers 150 terminate within backplane connector 112B. Other fibers not shown would terminate in other connectors, as might the free ends of fibers 150. In the illustrated embodiment, fibers that form a portion of the backplane 100 route optical signals between backplane connectors.
Fibers 152 connect at one end to optical components (not shown) on daughter card 120A. The other ends of these fibers terminate in daughter card connector 122A.
When electronic system 100 is assembled, daughter cards 120A and 120B are inserted into a card cage or other mechanical support system such that the daughter card connectors mate with the backplane connectors. Connectors that mate when pressed together are called “blind mate” connectors because there is no need for a person to have physical access to the connectors for proper mating. As they mate, the connectors provide alignment of the optical fibers so that optical signals readily pass from one daughter board to another through the backplane.
The connector system shown in FIG. 1 depicts the HD OPTX™ connector system sold by Teradyne, Inc. The system is constructed from modules. One type of module is a connector module, such as connector module 130.
Each connector module contains one or more ferrule carriers, such as 132. The ferrule carrier holds a ferrule (not shown) terminated onto a fiber optic cable to create a cable assembly. A ferrule is a precision manufactured component that holds the ends of optical fiber exposed at a surface and contains alignment features that allow two ferrules, when brought together, to precisely align the fiber ends.
The connector modules are held in a support member. In the daughter card connectors 122A and 122B, the connector modules are attached to a metal bar 134, sometimes called a “stiffener,” which acts as a support module. In backplane connectors, 122A and 112B, the connector modules are held in a housing 136, which might also be constructed of metal, and is the support module in the backplane connectors. Connectors of different sizes may be formed by using differently sized support modules.
The connectors also include latching modules. Daughter card connectors, 122A and 122B, include latching modules, such as latching module 162. Backplane connectors, 112A and 122B include latching modules, such as 164. Latching modules serve as a point of attachment of the connectors to the daughter card or the backplane. Each latching module has a surface pressed against the board. Attachment features on that surface are pressed into holes in the daughter card. The attachment features deform to make a tight fit in the holes to hold the daughter card connectors to the daughter card. Likewise, screws passing through the backplane engage the latching modules 164 in the backplane connectors and hold the backplane connectors to the backplane.
Latching module 162 includes a blade portion 166. Blade portion 166 fits into an opening in latching module 164 and engages features within latching module 164, thereby holding the connectors together. However, the preferred latching arrangement allows relative compliant motion between backplane connectors, such as 112A, and daughter card connectors, such as 122A. Compliance allows alignment features in the connectors and in the ferrules to dictate that final alignment of the optical fibers, even if there is some misalignment of the backplane and daughter cards.
FIG. 1 shows a portion of a backplane system. A typical electronic system might contain a card cage with more daughter cards than shown. Also, the system might include electrical connectors and many other components. FIG. 2 highlights the board-to-board optical connectors.
Further details of the modules of the connector system can be found in United States Patent Application 20040052472 to Roth, et al. entitled TECHNIQUES FOR FORMING FIBER OPTIC CONNECTIONS IN A MODULARIZED MANNER; United States Patent Application 20040008494 to Roth, entitled TECHNIQUES FOR CONNECTING A SET OF CONNECTING ELEMENTS USING AN IMPROVED LATCHING APPARATUS; United States Patent Application 20030044127 to Roth, et al., entitled, MODULAR FIBER OPTIC CONNECTION SYSTEM; United States Patent Application 20030044125 to Kiani, et al., entitled WAFERIZED FIBER OPTIC CONNECTOR; United States Patent Application to Kiani, et al., Ser. No. 10/744,050, entitled MODULAR FIBER OPTIC CONNECTOR SYSTEM; U.S. patent application Ser. No. 10/745,475 to Kiani, et al., entitled FIBER OPTIC BULKHEAD—all of the foregoing are hereby incorporated by reference.
While the backplane configuration is widely used in electronic systems, there are other known configurations. For example, in a matrix configuration, printed circuit boards are inserted from both sides of a card cage. The boards inserted from one side are orthogonal to the ones inserted from the other. The edge of each board inserted from one side is adjacent an edge of every board inserted from the other side. Electrical connectors have been developed that mount to these edges to move blind mate electrical connections from board to board. In other configurations, the circuitry on a board sends or receives signals through a cable that runs external to the card cage holding the printed circuit boards of an electronic system. To make electrical connections to a cable, a connector on a board in the electronic system might extend through an opening in a panel that forms a wall of an enclosure for the electronic system. Such connectors are known as panel mount connectors.
Though electrical connectors for matrix and panel applications are known, it would be desirable to have optical connectors that could be readily used in more applications, such as matrix configurations and panel configurations. It would be highly desirable to easily adapt connectors developed for backplane configurations to be used in other configurations.